This invention relates to an apparatus for the cold starting and warming run of externally ignited internal combustion engines and is of the type that electrically heats the fuel immediately adjacent the locus of injection and includes means which regulates its heat output in such a manner that the major portion of the fuel admitted for injection is transformed into a gaseous phase necessary for its combustion in the engine.
An apparatus of the aforenoted type has to avoid as much as possible or at least keep within permissible limits the emission of pollutants into the atmosphere for the protection of the environment and because of the ever stricter laws regarding air pollution.
It is known to heat the fuel under pressure to effect its vaporization upon expansion. Such a heating of the fuel prior to its admission in the suction tube is disclosed in German Patent Application Ser. No. D 71 833. Ia, while a heating of the fuel prior to its introduction into the combustion chamber is disclosed, for example, in German Pat. No. 905,902.
It is further known to enhance the heating of the fuel, in addition to the utilization of the engine heat and the exhaustion heat, by electrical heating means, as disclosed in German Pat. No. 929,884 or to effect such heating solely by electrical means, as disclosed in Austrian Pat. No. 197,133.
It is further known to control the heat output in accordance with the heat requirement as a function of the operational conditions of the engine, as disclosed in Austrian Pat. No. 127,239 and French Pat. No. 1,011,288.
It is, however, a common characteristic of all the aforenoted apparatuses which preheat fuel under pressure that they seek to facilitate the combustion of heavy oil in gasoline engines or they simply seek to improve the fuel preparation in Diesel engines and, even if they are concerned with the pressureless preheating of a mixture, cold starting and warm running must be ensured by additional means.
During cold starting of an engine, the fuel, the engine, as well as the fuel metering and preparing devices draw heat from the environment. Over the fuel there prevails, as over all liquids, a vapor pressure corresponding to its temperature and thus, the fresh combustion air flowing to the internal combustion engine is, dependent upon the vapor pressure and the period of contact, enriched with fuel vapor. At low temperatures this fuel concentration is not sufficient to form an ignitable mixture, so that for the same duration of contact a larger fuel surface has to be provided in order to reach the temperature limit of ignitability. In conventional cold starting apparatuses associated with carburetor or intake tube injection systems, this results in the introduction of fuel quantities during the period of cold starting that are 30-50 times more than those for normal operation. Consequently, there will be commensurate effects of pollutant emission, lubricating oil thinning and fuel consumption. During the warming run of the engine, these additional fuel quantities are then gradually decreased as the engine temperature increases, until the operating temperature of the engine has reached its normal value.